1. Field of the Invention
The present invention relates to a scrubbing apparatus for cleaning the surface of a substrate which has been subjected to film formation or polishing processing.
2. Description of the Prior Art
Significant defects occur in a patterned circuit of a semiconductor device when contamination such as particles, organic material and metallic ions are attached on the surface of a semiconductor wafer in a photolithographic process. Hence, it is very important to keep a wafer surface in a clean condition. For this reason, the wafer surface is cleaned in a photolithographic process any time when a necessity arises. For example, after a film formation process such as interlayer insulating film formation and a polishing process such as chemical mechanical polishing (hereinafter referred to as xe2x80x9cCMPxe2x80x9d), a wafer is rubbed by a brush while pouring a cleaning liquid on the wafer surface and contamination is thereby removed from the wafer surface. In such brush cleaning, a scrubbing apparatus with a spin chuck and a rotary brush is employed. The spin chuck is provided with a plurality of movable support members for supporting a wafer. When the spin chuck is rotated, an upper portion of the movable support members are inward inclined by a centrifugal force and put into contact with a circumferential portion of the wafer, so that the wafer is fast held so as not to get away from the spin chuck. In such a conventional brushing apparatus, however, since the brush collides against the movable support members, cleaning actions are required to progress so as to avoid such an interference. When cleaning is performed in such a brushing apparatus while avoiding the collision, a cleaning effect along the wafer circumferential portion comes to be short.
Recently, CMP has well been used as a processing technique for planarization of a pattern forming surface and when a pattern forming surface of a wafer is polished by CMP, much of foreign matter attaches along a peripheral portion of the wafer surface and on an edge surface of the wafer: such as particles resulted from a work itself, a polishing slurry and the like. For this reason, demand from users for cleaning the wafer peripheral portion to a sufficient extent has progressively been increased.
It is accordingly an object of the present invention is to provide a scrubbing apparatus for sufficiently cleaning a peripheral portion of a substrate.
A scrubbing apparatus according to the present invention comprises: a substrate support section for supporting a substrate horizontally and substantially in contact with a circumferential portion of the substrate while front side and back side surfaces of the substrate are substantially kept untouched in operation by the substrate; rotation drive means for driving the substrate support section to rotate in order to give a rotation force to the substrate; a brush member for scrub-cleaning the substrate while contacting at least the front side surface; a main nozzle provided with a first supply circuit for supplying a cleaning liquid in at least a central region of the substrate; an auxiliary nozzle provided with a second supply circuit for supplying the cleaning liquid in at least a peripheral region of the substrate; and an ultrasonic oscillator for applying ultrasonic waves to the cleaning liquid supplied on the substrate from an auxiliary nozzle.
A scrubbing apparatus according to the present invention comprises: control means for controlling the ultrasonic oscillator, wherein the control means, controls the ultrasonic oscillator so that the cleaning liquid supplied on the substrate from the main nozzle is also applied with ultrasonic waves and that a power of ultrasonic waves applied in the peripheral portion of the substrate is stronger than in the central region of the substrate and the cleaning liquid applied with ultrasonic waves is supplied not only in the peripheral region of the substrate from the auxiliary nozzle, but in the central region of the substrate from the main nozzle.
Since the cleaning liquid which is applied with ultrasonic waves penetrates into even a small gap with ease, every points on a substrate can be cleaned thoroughly. Therefore, the cleaning liquid can reach even a site which a brush member cannot contact, such as a clearance between a substrate support section and a substrate, and sufficient cleaning can be realized, perfectly covering the entire surface of the substrate by a cleaning acceleration action of ultrasonic waves.
Besides, since the substrate support section and the substrate are rotated in a relative manner, a contact site between both is constantly changed and therefore such a movement eliminates a site on the substrate where no cleaning occurs.